Dust cover for switches

ABSTRACT

An electrical switch having contact elements housed within an enclosure and including a shiftable actuator for the contacts extending outwardly from the enclosure through a slot in one wall thereof is protected against the entry of foreign particles by a double cover structure behind the slotted enclosure wall, including a slide cover on the actuator movable therewith and a stationary cover behind the slide cover with which the slide cover is in sliding contact. The slide cover is large enough to cover the actuator slot in all positions of the actuator; and as the slide cover shifts with the actuator it serves to expell from the enclosure through a pair of openings in opposite ends thereof dust and foreign particles which collect on the stationary cover.

United States Patent [191 Wilbrecht 1 I 3,723,692 51 Mar. 27, 1973 DUSTCOVER FOR SWITCHES [76] Inventor: Lester L. Wilbrecht, 45 Mid Oak Ln.,St. Paul, Minn. 55113 [22] Filed: June 7, 1972 [21] Appl. No.: 260,486

2,360,684 10/1944 Jennings ....200/168 G 3,211,877 10/1965 Walker et a1......200/168 G 2,878,347 3/1959 Schmidt ..200/168 H 2,829,222 4/1958Dunham ..200/168 H 2,158,317 Allen ..200/168 G Primary ExaminerH. 0.Jones Attorney-Ge0rge F. Williamson et al.

[57] ABSTRACT An electrical switch having contact elements housed withinan enclosure and including a shiftable actuator for the contactsextending outwardly from the enclosure through a slot in one wallthereof is protected against the entry of foreign particles by a doublecover structure behind the slotted enclosure wall, including a slidecover on the actuator movable therewith and a stationary cover behindthe slide cover with which the slide cover is in sliding contact. Theslide cover is large enough to cover the actuator slot in all positionsof the actuator; and as the slide cover shifts with the actuator itserves to expell from the enclosure through a pair of openings inopposite ends thereof dust and foreign particles which collect on thestationary cover.

8 Claims, 4 Drawing Figures DUST COVER FOR SWITCHES BACKGROUND OF THEINVENTION The problem of keeping the contacts of electrical switchesfree from dust, lint and foreign particles of all kinds is a continuingand serious one because such foreign matter can hold contacts open orclosed and otherwise interfere with the actuating mechanism of a switch.This problem is particularly acute on miniature switches now widelyemployed in miniaturized electronic circuits of various kinds. Thecontacts, contact space and actuating mechanism space on suchmicrominiature switches are so small that the presence of any foreignmatter is extremely likely to block the movement of contacts orotherwise interfere with their free actuation. Also, since the contactsof such miniature switches are frequently contained within an enclosurefrom which it is difficult if not impossible to extract dust or foreignparticles which enter, it is all the more important to not only preventthe entry of foreign matter into such switch enclosures, but also toprovide some means for periodically expelling foreign matter whichcollects on the switch actuator or its cover assembly before such mattercan find its way into the space where the contacts and actuatingmechanisms are contained. The switch closure structure of this inventionovercomes these problems and effectively prevents the entry of dust,dirt and foreign matter into the contact space of a switch.

BRIEF SUMMARY OF THE INVENTION The switch cover structure of thisinvention is particularly adapted for use with slide switches having aslide actuator for the contacts of the switch which projects outwardlythrough a slot in a closure wall within which the actuator is free toshift to various positions of use. The cover structure is particularlycharacterized by a double cover arrangement including a first, slidecover located under or behind the slotted wall of the switch enclosurethrough which the actuator extends and carried on the actuator formovement therewith. The slide cover is large enough to be in coveringrelation to the actuator slot in the enclosure wall at all operatingpositions of the actuator. A second, stationary cover is located behindthe slide cover and serves as a collecting surface for foreign matter toprevent its entry into the portion of the switch assembly housing thecontacts, the stationary cover'cooperating with the adjacent walls ofthe switch enclosure to close the end of the switch assembly throughwhich the actuator extends.

In a preferred embodiment of my cover structure, both the slide coverandthe stationary cover are planar members, the stationary cover havinga slot therein in alignment with the actuator slot in the enclosure walland of sufficient length to accommodate the full, shifting stroke of theactuator to its operational positions. The slide cover and thestationary cover are preferably separate, removable elements with theslide cover being removably attached to the actuator by an aperturetherein whichvsnuggly embraces the actuator and through which theactuator and its outer, gripping head or knob extend.

A particularly advantageous feature of the cover structure resides inthe provision of a pair of opposed openings in the switch enclosure inalignment with the slide cover and the stationary cover, whereby anyforeign particles accumulating on the stationary cover will be expelledfrom opposite ends of the enclosure through said opposed openings by theopposite ends of the slide cover as it reciprocates with the actuator onthe stationary cover. By virtue of this cover structure arrangement,dust, lint and foreign particles which periodically accumulate on top ofthe stationary cover are expelled from the switch enclosure before theyhave an opportunity to find their way into the contact containing spaceof the switch assembly.

These and other objects and advantages of my invention will becomereadily apparent as the following description is read in conjunctionwith the accompanying drawings wherein like reference numerals have beenused to designate like elements throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top, plan view of a switchassembly incorporating the cover structure of this invention;

FIG. 2 is a vertical section view taken along lines 2 2 of FIG. 1;

FIG. 3 is a right end view of the switch and cover structure of FIG. 1;and

FIG. 4 is a vertical section view taken along lines 4- 4 of FIG. 1.

DESCRIPTION OF THE PREFERRED' EMBODIMENT Referring now to the drawings,I have shown in FIGS. 1 through 4 a slide action switch of the generaltype for which the dust cover of this invention has been particularlydeveloped. The entire switch assembly is generally indicated byreference numeral 1, and includes an enclosure comprised of a housing 2made of insulating material and a closure frame 4 of inverted, U-shapewhich is mounted in closing relation to the open, top end of housing 2.Housing 2 includes a base wall 2a, upstanding end walls 2b and opposed,upstanding side walls 20. Closure frame 4 includes a generally planar,top closure wall 4a and a pair of downwardly depending wall segments 4bat opposite ends thereof. Wall segments 4b extend downwardly inoverlying relationto opposed end walls 2b 'of housing 2 and cooperatetherewith in providing a complete switch enclosure. Closure frame 4 issecured to housing 2 by means of lock tabs 4c at the bottom of wallsegments 4b which engage the underside of base wall 2a of housing 2.

Positioned on base wall 2a of housing 2 is a conductor insert 6 having aplurality of conductor strips 6a, 6b, 6c, and 6d projecting outwardlyfrom housing 2 for connection within an electrical circuit. The switchassembly 1 disclosed herein is of the micro-miniature type' designed foruse in electronic circuits in combination with other miniatureelectronic components. For

such applications, switch assembly 1 is on the order of three-quartersof an inch in length, 5 1 inch in height, and V4 inch in width. Thus,the switch operating and contact space within housing 1 is quite small.

The inner ends of conductor strips 6a, 6b, 6c and 6d are positionedwithin housing 2 to form contacts which are located to be bridged by apair of contact springs 8 and 10 extending lengthwise along base wall 2aon opposite sides thereof. The inner ends of contact strips6a,

6b, 6c and 6d may obviously be positioned in cooperative relation withthe contact ends of contact springs 8 and 10 to provide any desiredswitch and circuit arrangementpFor example, the inner ends of contactstrips 6b and 6c may be positioned for bridging by contact spring 8 withthe inner ends of contact strips 6a and 6d angled inwardly to be bridgedby the opposite ends of contact spring 10. Contact ends 8a and 8b ofcontact spring 8 are shown in FIG. 2. Various operating mechanisms maybe employed in order to actuate contact springs 8 and 10 into a closedposition with the inner, contact ends of strips 6a, 6b, 6c and 6d. Forillustrative purposes I have shown an actuating mechanism comprised of adriver plate 12 slidably positioned on top of base wall 2a and a slideacutator 14 having a driver head portion 15 slidably positioned withinhousing 2 and a gripping head or knob portion 16 projecting outwardlytherefrom. Actuator 14 is slidably shiftable within housing 1 andincludes a pair of pick-up fingers 17 and 18 depending downwardly fromits driver head 15 which are positioned to engage and slidably movedriver plate 12 as actuator 14 is shifted in opposite directions. Eachof the contact springs 8 and 10 is provided with upwardly projectingdetents 20 aligned with driver plate 12 so that as plate 12 is shiftedback and forth, end or shoulder portions provided thereon atpredetermined locations will engage detents 20 and urge the contact endsof springs 8 and 10 downwardly into closing position with the inner endsof contact strips 6a, 6b, 6c and 6d. Thus, as actuator 14 is shiftedfrom the left or off position as viewed in FIG. 2 to the right, theright end of driver plate 12 will engage the right detent 20 of contactspring 8 and urge its contact end 8b downwardly into contact with theinner end of contact strip 60. With the opposite contact 8a of contactspring 8 held downwardly against contact strip 6b, the inner ends ofstrips 6b and 60 will be bridged by contact spring 8 and a circuit willbe established across these contact points. In a similar manner, contactspring 10 will be urged downwardly at its opposite ends by the slidingaction of driver plate 12 to bridge contacts 6a and 6d.

Actuator 14 may be positioned and guided for various types of movementalong linear or arcuate paths. In the switch assembly illustratedherein, actuator 14 is guided for linear movement to permit its sliding,reciprocal action by means of a rectangular slot 22 provided in top,closure wall 4a of closure frame 4. Gripping knob 16 of actuator 14projects upwardly through slot 22, the length of slot 22 being such asto accommodate a shifting stroke of actuator 14 sufficient to open andclose contacts contained within housing 2 as desired. Elongated slot 22obviously presents an opening through which dust, lint and foreignparticles of various kinds might pass into switch housing 2 as grippingknob 16 is shifted back and forth. I order to prevent the entry of such,foreignmatter into the switch operating and contact space withinhousing 2, I have provided a cover structure comprised of a pair ofplanar cover members 24 and 26. Cover 24 is a slide cover positioned ongripping knob 16 of actuator 14 and slidably shiftab'le therewith.Although slide cover 24 may be attached to actuator 14 in various ways,I have found 'it convenient to accomplish'this by providing an aperturevin slide cover 24 which tightly and snuggly embraces gripping head 16and through which gripping head 16 extends. Slide cover 24 is removablyattached to gripping head 16 by sliding it thereover in a force fittherewith. Slide cover 24 is positioned under or behind closure-wall 4aof closure frame 4 and extends longitudinally on opposite sides ofgripping knob 16 by a distance sufficient to project beyond the opposed,transverse edges 22a and 22b. of slot 22 in covering relation thereto atall operational positions of actuator 14. Slide cover 24 is also ofgreater width than slot 22 to thereby serve as a closure device withrespect to this slot.

Cover 26 is positioned behind slide cover 24 and is a stationary coverwith which slide cover 24 is positioned in sliding engagement. Theperipheral edges of stationary cover 26 abutt against the insidesurfaces of adjacent wall portions 2b and 2c of housing 2 and cooperatetherewith, as well as with slide cover 24, to close the open, upper endof housing 2. Stationary cover 26 is provided with a central aperture orslot 28 in alignment with slot 22 in closure wall 4a and of sufficientlength to accommodate the full, shifting stroke of actuator 14 to itsvarious operational positions, gripping knob 16 extending through slot28 as well as through aligned slot 22. Stationary cover 26 is removablypositioned in place on housing 2 by placing it over actuator 14 and itsgripping knob 16. Cover 26 is supported along its side edges onelongated shoulders 30 and 31 provided on the inside, upper surface ofside walls 2c of housing 2, in the manner illustrated in FIG. 4. At itsopposite ends, stationary cover 26 rests on upright housing ribs 32 and33 and on a pair of removable spacers 34 and 35. As may be most clearlyunderstood by reference to FIG. 4, spacers 34 and 35 extend alongopposed side walls 20 of housing 2 in abutting contact therewith andprovide sliding support for laterally projecting shoulders 36 and 37 onactuator 14, as well as serving to space and support actuator 14 at thedesired vertical location within housing 2.

As driver head 15 of actuator 14 is slidably shifted back and forthwithin housing 2, it is supported on the top surface of spacers 34 and35, the alternate engagement of depending pick-up fingers l7 and 18 withopposite ends or shoulders of driver plates 12 serving to open and closethe contacts contained within housing 2. A snap action is imparted toactuator 14, and to the closing of the switch contacts, by utilizing apair of detent springs 38 and 39. Detent springs 38 and 39 extendlongitudinally within housing 2 on opposite sides of driver head 15 andinclude a pair of inwardly projecting detents which cooperate withoutwardly projecting lugs on opposite sides of driver head 15 to providea snap action to actuator 14 as it is shifted back and forth. The springdetents and cooperating lugs on driver head 15 are not shown in thedrawings as they comprise no part of the dust cover invention to whichthis application is directed. Reference is made to my copendingapplication entitled Snap-Action Switch Mechanism, filed on June 12,I972 under Ser. No. 262,052, for a clear understanding of the switchoperating mechanism including the cooperative relation of the springdetents with.

tially be lodged on slide cover 24, and if any of these foreignparticles should fall off the opposite ends of slide cover 24 as itreciprocates back and forth, they will be caught on stationary cover 26lying thereunder. In this manner, the cover assembly permits the full,reciprocating action of actuator 14 while preventing the entry offoreign matter into the contact containing space of housing 2. It willbe appreciated that any small foreign particles finding their way intothe interior of housing 2 could have the adverse effect of blocking thecontact ends of contact springs 8 or 10 in an open or closed position.

The covering action of slide cover 24 and stationary cover26 is furtherenhanced by forming cover 26 to a channel shape defined by opposed,upright side walls 26a and 26b clearly illustrated in FIG. 4. Theopposed, side edges of slide cover 24 are in sliding engagement withside wall portions 26a and 26b of stationary cover 26, as well as withits base or bottom wall, whereby the stationary cover 26 serves as aguiding device for slide cover 24 and cooperates with it in forming arelatively tight seal to prevent the entry of foreign particles into theswitch enclosure.

As a particularly advantageous feature of my dust cover structure for aswitch assembly, apertures are provided at the opposite ends of theenclosure through which dust, lint and foreign particles accumulating onstationary cover 26 may be periodically expelled from the enclosure. Forthis purpose, a pair of opposed end openings are provided in theenclosure end walls in alignment with slide cover 24 and stationarycover 26. These end openings are defined by apertures 40 and 41 formedin the opposite ends of closure frame 4, and by notches 42 and 43 ofequal extent with apertures 40 and 41 formed in housing end walls 2b.Housing end notches 42 and 43 and closure frame apertures 40 and 41 arein horizontal alignment with each other so as to cooperativelydefinecontinuous end openings in the enclosure through wich foreign particlesmay be ejected. The upper faces of stationary dust cover 26 on oppositeends of slot 28 therein serve as dust collecting surfaces on which dustparticles, lint and small foreign particles of any kind accumulate afterpassing through slot 22 in upper closure wall 4a. Because of the slidingengagement of slide cover 24 with cover 26, dust and foreign particlescollecting on the top faces of stationary dust cover 26 willperiodically be picked up by the opposite ends of slide cover 24 as itreciprocates with actuator 14 and ejected from the switch assemblyenclosure through'the end openings defined by closure frame slots 40, 41and housing end wall notches 42, 43. Slide cover 24 thus serves as adust, lint and foreign particle ejector, as well as a covering device.The ejecting action of slide cover 24 thus periodically expells foreignparticles accumulating on stationary cover 26 from the switch enclosure,thereby greatly minimizing the likelihood that any foreign particleswill find their way into the inner confines of the switch enclosurewherein the switch contacts are located.

While I have described and shown a preferred embodiment of my dustclosure structure herein, 1 contemplate that various changes may be madein the size, shape and construction of the cover components withoutdeparting from the spirit and scope of my invention as defined by. thefollowing claims.

I claim:

slot, on said actuator and shiftable therewith, said slide cover beingpositioned behind said closure wall and having sufficient length to bein closing relation to said slot at all operational positions of saidactuator;

a stationary cover behind said slide cover with which said slide coveris in sliding engagement,. the peripheral edges of said stationary covercooperating with the adjacent walls of said enclosure to close said oneend of said enclosure; and

a slot in said stationary cover in alignment with said slot in saidclosure wall and of sufficient length to accommodate the full shiftingstroke of said actuator to its operational positions.

2. A switch and cover structure as defined in claim 1 wherein:

said stationary cover is of channel shape defined by a 30 planar bottomwall and upright side walls against which said slide cover is in slidingcontact,

whereby said stationary cover serves as a guiding device for said slidecover and cooperates therewith in forming a seal to prevent the entry offoreign particles into said enclosure. 3. A switch and cover structureas defined in claim 1 wherein:

said slide cover and said' stationary cover are of planar shape and saidactuator is reciprocally shiftable within said closure wall slot; and apair of opposed end openings in said enclosure in alignment with saidslide cover and said stationary cover, whereby any foreign particlesaccumulating on said stationary cover will be expelled from saidenclosure through said end openingsby the opposite endsof said slidecover as it reciprocates with said actuator on said stationary cover. 4.A switch and cover structure as defined in claim 3 wherein:

said closure wall is part of a closure frame of inverted, U-shape havinga pair of depending wall segments cooperating with opposed end wallportions of said enclosure to enclose said electrical contact elements,said wall segments of said closure frame having apertures thereindefining at least a portion of said end openings in said enclosurethrough which foreign particles are expelled. 5. A switch and coverstructure as defined in claim 1 wherein:

separate, removable elements, said slide cover being removably attachedto said actuator gripping head by an aperture therein which snugglyembraces said actuator gripping head and through which said actuatorgripping head extend. 6. An enclosed switch assembly comprising incombination:

said slide cover and said stationary cover are an enclosure having aclosure wall over one end thereof with an elongated slot therein;electrical contact elements contained within said enclosure and movableinto and out of contact with each other; an actuator having a firstportion thereof within said enclosure operatively associated with saidcontact elements and a second, gripping knob portion thereof extendingout of said enclosure through said slot in said closure wall, saidactuator being slidably reciprocal within said vslot; slide cover onsaid actuator movable therewith, said slide cover being positionedbehind said closure wall and extending longitudinally on opposite sidesof said actuator by a distance sufficient to project beyond the opposed,transverse edges of said slot in covering relation thereto at alloperational positions of said actuator, and said slide cover being ofgreater width than said slot; planar, dust collecting surfaces behindsaid slide cover with which said slide cover is in sliding engagement,said dust collecting surfaces being disposed adjacent opposed end wallsof said enclosure towards which said actuator slides .as itreciprocates; and

an aperture in each of said enclosure end walls in alignment with saidslide cover, whereby dust and foreign particles collected on said planarsurfaces are picked up by the ends of said slide cover as itreciprocates and ejected from said enclosure through said apertures insaid end walls.

7. An enclosed switch assembly as defined in claim 6 wherein; u

said planar, dust collecting surfaces are portions of a stationary coverand are spaced apart by a slot therein in alignment with said slot insaid closure wall and of sufficient length to accommodate the fullshifting stroke of said actuator to its operational positions.

8. In combination with a switch actuator, a cover structure for anelectrical switch mechanism for preventing the entry of foreignparticles into the switch operating and contact space, comprising:

a closure member with an elongated slot therein through which saidactuator extends, said actuator being reciprocally shiftable within saidslot;

a slide cover of greater length and width than said closure member sloton said actuator and shiftable therewith, said slide cover beingpositioned behind said closure member and having sufficient length to bein closing relation to said slot at all operational positions of saidactuator;

a stationary cover behind said slide cover with which said slide coveris in sliding engagement, said stationary cover having a slot therein inalignment with said slot in said closure member and of sufficient lengthto accommodate the full shifting stroke of said actuator to itsoperational positions; and

opposed, open spaces at the opposite ends of said closure member inalignment with said slide cover and said stationary cover wherebyforeign particles accumulating on said stationary cover are picked up bytheopposite ends of said slide cover as it reciprocates with said switchactuator and are expelled through said open spaces.

1. On a switch including an enclosure within which electrical contactelements are housed, and a shiftable actuator for said contact elementsprojecting outwardly from said enclosure, an improved cover structureaccommodating the shifting movement of said actuator comprising: aclosure wall with an elongated slot therein over one end of saidenclosure, said actuator extending through said slot and terminating atits outer end at a gripping head for shifting movements within saidslot; a slide cover of greater length and width than said slot, on saidactuator and shiftable therewith, said slide cover being positionedbehind said closure wall and having sufficient length to be in closingrelation to said slot at all operational positions of said actuator; astationary cover behind said slide cover with which said slide cover isin sliding engagement, the peripheral edges of said stationary covercooperating with the adjacent walls of said enclosure to close said oneend of said enclosure; and a slot in said stationary cover in alignmentwith said slot in said closure wall and of sufficient length toaccommodate the full shifting stroke of said actuator to its operationalpositions.
 2. A switch and cover structure as defined in claim 1wherein: said stationary cover is of channel shape defined by a planarbottom wall and upright side walls against which said slide cover is insliding contact, whereby said stationary cover serves as a guiDingdevice for said slide cover and cooperates therewith in forming a sealto prevent the entry of foreign particles into said enclosure.
 3. Aswitch and cover structure as defined in claim 1 wherein: said slidecover and said stationary cover are of planar shape and said actuator isreciprocally shiftable within said closure wall slot; and a pair ofopposed end openings in said enclosure in alignment with said slidecover and said stationary cover, whereby any foreign particlesaccumulating on said stationary cover will be expelled from saidenclosure through said end openings by the opposite ends of said slidecover as it reciprocates with said actuator on said stationary cover. 4.A switch and cover structure as defined in claim 3 wherein: said closurewall is part of a closure frame of inverted, U-shape having a pair ofdepending wall segments cooperating with opposed end wall portions ofsaid enclosure to enclose said electrical contact elements, said wallsegments of said closure frame having apertures therein defining atleast a portion of said end openings in said enclosure through whichforeign particles are expelled.
 5. A switch and cover structure asdefined in claim 1 wherein: said slide cover and said stationary coverare separate, removable elements, said slide cover being removablyattached to said actuator gripping head by an aperture therein whichsnuggly embraces said actuator gripping head and through which saidactuator gripping head extend.
 6. An enclosed switch assembly comprisingin combination: an enclosure having a closure wall over one end thereofwith an elongated slot therein; electrical contact elements containedwithin said enclosure and movable into and out of contact with eachother; an actuator having a first portion thereof within said enclosureoperatively associated with said contact elements and a second, grippingknob portion thereof extending out of said enclosure through said slotin said closure wall, said actuator being slidably reciprocal withinsaid slot; a slide cover on said actuator movable therewith, said slidecover being positioned behind said closure wall and extendinglongitudinally on opposite sides of said actuator by a distancesufficient to project beyond the opposed, transverse edges of said slotin covering relation thereto at all operational positions of saidactuator, and said slide cover being of greater width than said slot;planar, dust collecting surfaces behind said slide cover with which saidslide cover is in sliding engagement, said dust collecting surfacesbeing disposed adjacent opposed end walls of said enclosure towardswhich said actuator slides as it reciprocates; and an aperture in eachof said enclosure end walls in alignment with said slide cover, wherebydust and foreign particles collected on said planar surfaces are pickedup by the ends of said slide cover as it reciprocates and ejected fromsaid enclosure through said apertures in said end walls.
 7. An enclosedswitch assembly as defined in claim 6 wherein: said planar, dustcollecting surfaces are portions of a stationary cover and are spacedapart by a slot therein in alignment with said slot in said closure walland of sufficient length to accommodate the full shifting stroke of saidactuator to its operational positions.
 8. In combination with a switchactuator, a cover structure for an electrical switch mechanism forpreventing the entry of foreign particles into the switch operating andcontact space, comprising: a closure member with an elongated slottherein through which said actuator extends, said actuator beingreciprocally shiftable within said slot; a slide cover of greater lengthand width than said closure member slot on said actuator and shiftabletherewith, said slide cover being positioned behind said closure memberand having sufficient length to be in closing relation to said slot atall operational positions of said actuator; a stationary cover behindsaid slide cover with which said slide cover is in sliding engagement,said stationary cover having a slot therein in alignment with said slotin said closure member and of sufficient length to accommodate the fullshifting stroke of said actuator to its operational positions; andopposed, open spaces at the opposite ends of said closure member inalignment with said slide cover and said stationary cover wherebyforeign particles accumulating on said stationary cover are picked up bythe opposite ends of said slide cover as it reciprocates with saidswitch actuator and are expelled through said open spaces.